HP 438031-B21 - 1:10Gb Ethernet BL-c Switch Application Manual page 105

For example, consider the following topology migration:
Figure 14 Router legacy network
In this example, a corporate campus has migrated from a router-centric topology to a faster, more
powerful, switch-based topology. As is often the case, the legacy of network growth and redesign has left
the system with a mix of illogically distributed subnets.
This is a situation that switching alone cannot cure. Instead, the router is flooded with cross-subnet
communication. This compromises efficiency in two ways:
Routers can be slower than switches. The cross-subnet side trip from the switch to the router and back
again adds two hops for the data, slowing throughput considerably.
Traffic to the router increases, increasing congestion.
Even if every end-station could be moved to better logical subnets (a daunting task), competition for
access to common server pools on different subnets still burdens the routers.
This problem is solved by using HP 1:10GbE switch with built-in IP routing capabilities. Cross-subnet LAN
traffic can now be routed within the switches with wire speed Layer 2 switching performance. This not
only eases the load on the router but saves the network administrators from reconfiguring each and every
end-station with new IP addresses.
Basic IP routing
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